Building Code and Safety Guides: IRC, OSHA, ADA

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Most building questions end with a number: how big a bedroom window must be, how steep a ramp can be, how far a ladder foot goes out, how much air a bathroom fan has to move. These 35 guides each take one of those questions, state the rule and where it comes from, and do the arithmetic for you, often with a small checker or calculator on the page. They sit alongside our calculators, which handle quantities and cut lists, and the thread and fastener charts.

The guides are grouped by the rule book they come from. Codes are adopted and amended locally, OSHA rules apply to employers, and the ADA Standards apply to public and commercial buildings, so each group starts with a note on when its rules apply to you.

Residential building code (IRC)

Plain-language summaries of the International Residential Code rules a homeowner or remodeler meets most often. Your city or county adopts a particular edition and may amend it, so treat these as a starting point and confirm with the local building department before you build.

  • Egress window size: the clear opening area, height, width and sill height a bedroom or basement escape window needs (IRC R310), with a checker for your window.
  • Handrail and guard height: stair handrail height, deck and porch guard height, and baluster spacing, compared with the commercial, ADA and OSHA heights.
  • Ceiling height, room size and hallway width: the minimum dimensions for habitable rooms, ceilings, hallways and the egress door.
  • Toilet clearance and rough-in: side and front clearances, spacing between toilets, and how to measure a rough-in before buying a toilet.
  • Attic ventilation: net free vent area from the 1/150 and 1/300 rules (IRC R806.2), split between soffit intake and ridge exhaust.
  • Concrete slab thickness: the code minimum for floors and the usual thickness for patios, sheds, garages and driveways.
  • Drywall sizes and thickness: which board goes on walls, ceilings, garages and bathrooms, including where fire-rated Type X is used.

Job-site safety (OSHA)

The federal OSHA rules in 29 CFR 1926 (construction) and 1910 (general industry) that apply to ladders, trenches, scaffolds, stairs, fall protection and noise. Each guide quotes the rule, explains it, and works the numbers for you.

  • Ladder angle and the 4-to-1 rule: how far to set the base out, how long a ladder you need to reach a roof, and the federal ladder rules.
  • Trench sloping: maximum slopes for stable rock and Type A, B and C soil, top width by depth, and when a trench needs protection.
  • Scaffold requirements: the 4:1 tie rule, platform width, plank overhang, guardrails and access.
  • Fall protection height: the trigger heights for construction, general industry and scaffolds, and the clearance a fall arrest system needs.
  • Stair requirements: stair angle, riser and tread limits, and handrail and stair rail heights.
  • Noise exposure: permissible hours by sound level, the stricter NIOSH limit, and a daily noise dose calculator for shop tools.

Accessibility (2010 ADA Standards)

Dimensions from the 2010 ADA Standards for Accessible Design, which apply to public accommodations, commercial facilities and state and local government buildings, and are a sensible reference for a home being adapted for a wheelchair user.

  • Ramp slope: the 1:12 maximum slope, ramp length by rise, landings, and every other ramp requirement.
  • Door width and clearance: the 32 in clear width, which door size provides it, maneuvering space, thresholds and hardware.
  • Grab bar height and placement: mounting height, diameter, wall spacing and length at toilets, tubs and showers.
  • Counter and sink height: work surfaces, sinks and service counters, with knee and toe clearance and reach ranges.

Ventilation, water heating and energy

Sizing rules from the Home Ventilating Institute, ENERGY STAR and the Department of Energy for fans, water heaters, insulation and windows.

Materials and size charts

Reference charts for buying and laying out materials: what the size numbers mean, how much to order, and the spacing rules that go with them.

  • Rebar size chart: diameter, area and weight of #3 to #18 bar, with metric equivalents.
  • Concrete curing time: strength by day, when to walk or drive on new concrete, and cold-weather precautions.
  • Gravel sizes: what #57, #67, #8 and other crushed stone numbers mean and which to use where.
  • Roofing squares and bundles: shingle bundles by roof size and pitch, plus starter, ridge, nails and underlayment.
  • Deck board spacing: gaps for wet treated, kiln-dried and composite boards, worked out from shrinkage data.
  • Fence post depth and spacing: hole depth, post spacing and size, and concrete per hole.
  • Tile spacing: grout joint widths by tile size and the offset rule for large-format tile.
  • Crown molding angles: miter and bevel settings for common crown angles at any corner.
  • Sheet metal gauge: thickness of steel, galvanized, stainless and aluminum by gauge, and sheet weights.
  • Wire gauge (AWG): diameter, area, resistance and weight of copper and aluminum wire.

How to use these guides safely

  • Check the local edition. The IRC is a model code. Each state or city adopts an edition (often several years old) and may change it, so the permit office has the final word on dimensions and inspections.
  • Structural work needs a design. Beams, footings, retaining walls, guards and anything that holds people up should be sized from the adopted code tables or by an engineer. Our pages explain the rules; they do not replace the plan review.
  • Safety rules are minimums. OSHA and ADA figures are the least that is allowed. Where a guide gives a range, the safer end is usually also the easier one to inspect.
  • Tell us about mistakes. Each guide lists its sources and a review date. If a number disagrees with your code or a newer edition, please write to us and we will check and correct it.

Last reviewed: 25 October 2026. How we build and check our pages: methodology and corrections. Spotted an error? Please let us know.